Harden prompt debug redaction

internal/adapters/promptkit/adapter_test.go

@@ -316,6 +316,30 @@ func TestExecuteCapturesSensitiveDebugOnlyWhenRequested(t *testing.T) {
 	}
 }
 
+func TestMarshalDebugParametersOmitsProviderExtras(t *testing.T) {
+	const marker = "private-debug-marker"
+	parameters := string(marshalDebugParameters(promptkit.ExecutionTarget{
+		Temperature:     0.2,
+		MaxTokens:       400,
+		TopP:            0.9,
+		TimeoutSeconds:  30,
+		ServiceTier:     "flex",
+		ReasoningEffort: "high",
+		ExtraParams: map[string]any{
+			"access-key": marker,
+			"signature":  marker,
+		},
+	}))
+	if strings.Contains(parameters, marker) || strings.Contains(parameters, "extra_params") {
+		t.Fatalf("debug parameters leaked provider extras: %s", parameters)
+	}
+	for _, want := range []string{`"temperature":0.2`, `"max_tokens":400`, `"top_p":0.9`, `"timeout_seconds":30`, `"service_tier":"flex"`, `"reasoning_effort":"high"`} {
+		if !strings.Contains(parameters, want) {
+			t.Fatalf("debug parameters missing safe value %q: %s", want, parameters)
+		}
+	}
+}
+
 func TestExecuteCallbackFailurePreventsGeneration(t *testing.T) {
 	client := &fakeClient{response: validResponse()}
 	adapter := newTestAdapter(t, client)